window.onload = function () {
    var minSize = 5; //最小字体
    var maxSize = 50;//最大字体
    var newOne = 100; //生成雪花间隔
    var flakColor = "#fff"; //雪花颜色
    var flak = $("<div></div>").css({position:"absolute","top":"0px"}).html("❉");//定义一个雪花
    var dhight = $(window).height(); //定义视图高度
    var dw =$(window).width()-80; //定义视图宽度
    setInterval(function(){
    var sizeflak = minSize+Math.random()*maxSize; //产生大小不等的雪花
    var startLeft = Math.random()*dw; //雪花生成是随机的left值
    var startOpacity = 0.7+Math.random()*0.3; //随机透明度
    var endTop= dhight-100; //雪花停止top的位置
    var endLeft= Math.random()*dw; //雪花停止的left位置
    var durationfull = 5000+Math.random()*5000; //雪花飘落速度不同
    flak.clone().appendTo($("body")).css({
    "left":startLeft ,
    "opacity":startOpacity,
    "font-size":sizeflak,
    "color":flakColor
    }).animate({
    "top":endTop,
    "left":endLeft,
    "apacity":0.1
    },durationfull,function(){
    $(this).remove()
    });
    },newOne);
}